This invention generally relates to fluid springs such as pneumatic or airsprings, of the type used in fluid suspension systems. More particularly this invention relates to fluid springs of the type in which a piston moves within a flexible resilient member or sleeve to cause compression and expansion of the confined fluid. Such airsprings are commonly known as reversible sleeve or rolling lobe type airsprings as distinguished from bellows type airsprings.
In a rolling lobe type airspring at least one of the elements to which the flexible member is secured is a generally cylindrical piston usually made of metal or plastic and which is employed to cause compression and expansion of the fluid contained in the spring. When a load is applied axially (that is, in the lengthwise direction) of this type of spring the piston moves within the flexible member which reverses upon itself to form a rolling lobe which rolls over the piston. The resulting change in the configuration of the spring member consequently changes the pressure of the fluid contained in the chamber. The outer surface of the piston over which the lobe of the flexible member rolls as well as the rest of the components of the airspring are carefully engineered to provide the desired operating characteristics. Variation in the surface over which the rolling lobe travels during operation of the airspring results in undesired deviations from the air spring's design characteristics.
In known rolling lobe airsprings, the flexible tubular member comprises a generally cylindrical member of elastomeric material having reinforcements therein at least one end of the flexible member typically is of tapering thickness upon completion of the molding operation. When the flexible member is secured to the piston this tapered end may extend into the working area of the piston contour causing a noticeable and undesired change in the fine tuned characteristics of the airspring. Another problem with this known airspring design is that the rolling lobe of the flexible member may in service repeatedly roll over the tapered end portion of the flexible member which lies on the piston surface resulting in rubber reversion or chemical breakdown whose tacky nature may cause undesirable dirt and foreign material build-up on the piston working area. Such build-ups will change the airspring's characteristics and may reduce its service life.
It is an object of the invention to provide a rolling lobe airspring employing a tubular flexible member which substantially reduces or eliminates the possibility of variation from the design characteristics of the airspring.
It is another object of the invention to provide a tubular flexible member rolling lobe airspring in which the possibility of undesirable piston build-up to the rubber reversion or chemical breakdown is substantially reduced or eliminated.